Cigarette smoking is the leading cause of preventable death in the United States, and in the world. Unfortunately, quitting isn’t easy. At best, only one out of three people who try nicotine replacement therapy (NRT) or the antidepressant drug bupropion (two of the most popular drugs used to help quit smoking) are still cigarette-free after one year. Those who use NRT may still experience nicotine withdrawal symptoms, and some may even become dependent on NRT–particularly when used as a nasal spray.
In May 2006, the US Food and Drug Administration (FDA) approved a new drug, varenicline tartrate (Chantix), to help smokers quit smoking. Scientists based the structure of varenicline on a plant-based medicine that Eastern Europeans have used for decades for smoking cessation. Nicotine binds to receptors in the brain that release dopamine, which causes the pleasurable feelings that make smokers want to come back for more. Varenicline binds to the same receptors in the brain, but only releases a fraction of the dopamine that nicotine does. As a result, varenicline can reduce cravings without leading to an addiction of its own.
In two articles published in the August 14/28
Archives of Internal Medicine
, researchers studied the effectiveness, tolerability, and safety of varenicline for smoking cessation. They found that varenicline was significantly more effective than placebo at helping smokers quit without relapse, both in the short- and long-term, and that the drug was safe and well-tolerated.
About the Study
In the first study, the researchers randomly assigned healthy smokers, ages 18-65 years, to brief behavioral counseling and one of five treatments: 0.3 milligrams (mg) varenicline once daily for six weeks plus one week of placebo; 1.0 mg varenicline once daily for six weeks plus one week of placebo; 1.0 mg varenicline twice daily for six weeks plus one week of placebo; 150 mg bupropion twice daily for seven weeks; or placebo for seven weeks.
Based on daily diaries maintained by the study subjects as well as weekly breath analysis, the researchers recorded how many smokers did not smoke for at least four continuous weeks (continuous quit rate, or CQR) during the seven-week treatment phase, and then for up to 52 weeks while off treatment. Study participants reported any cravings and adverse effects.
In the second study, the researchers studied the effects of gradually increasing the dose of varenicline up to 0.5 mg or 1.0 mg twice daily for twelve weeks, compared to placebo.
In the first study, participants who took 1.0 mg varenicline once or twice daily had significantly higher continuous quit rates during the treatment phase than participants taking a placebo. Participants taking 1.0 mg varenicline twice daily were also significantly more likely to be cigarette-free at week 52, and had significantly fewer cravings at all points during the study, compared to participants taking a placebo. Varenicline did not significantly affect withdrawal symptoms.
The second study also found that participants taking varenicline had significantly higher smoking cessation rates, compared to placebo. This study used a different definition of abstinence than did the first study: seven recent consecutive days free of smoking confirmed by breath carbon monoxide studies.
Quit rates were higher at one year than in the first study, but there was a significant relapse rate after 12 weeks. In addition, at least 60% of the subjects dropped out of the study before the one year follow-up visit. It is possible that an even higher proportion of drop-out subjects had restarted smoking than was the case for those who continued to make study visits. If this were the case, the long-term effectiveness of varenicline would have been different from what the authors reported.
These studies were designed and conducted by Pfizer, the pharmaceutical company that makes and sells varenicline.
How Does This Affect You?
In these studies, varenicline was significantly more effective than placebo at helping smokers quit, though at one year fewer than 15% of smokers met the study’s definition of abstinence (28 days of reported freedom from cigarettes plus confirmation by breath analysis).
While bupropion seemed less effective than varenicline in this study, smokers who had failed previous treatment with bupropion were allowed to take part in this study (and some were randomly assigned to take bupropion again). Since this study design may have made varenicline only appear to be more effective than bupropion, if you have not previously tried bupropion you and your doctor may want to weigh cost and side effects before deciding which drug to choose. Remember too that all of the participants in these studies received at least eight weekly sessions of “brief behavioral counseling” as well as drugs. Additional counseling was offered at follow-up appointments after treatment stopped.
Counseling–even by telephone–has been shown to increase quit rates, especially when used along with nicotine replacement therapy or bupropion. Remember, too, that because varenicline blocks the brain effects of nicotine it can’t be used along with nicotine replacement therapy–though future studies might ask whether following seven weeks of varenicline with NRT might further increase quit rates.
Smoking has been linked to various cancers, heart disease, and lung disease. If you smoke and want to quit, even if you’ve tried to quit and failed in the past, talk to your physician right away. Varenicline might be just what you need to become an ex-smoker.
Etter J-F. Cytisine for smoking cessation: a literature review and a meta-analysis.
Arch Intern Med
. 2006; 166:1553-1559.
Johnson BA. New weapons to curb smoking: no more excuses to delay treatment. [Editorial.]
Arch Intern Med.
Nides M et al. Smoking cessation with varenicline, a selective alpha4β2 nicotinic receptor partial agonist: results from a 7-week, randomized, placebo and bupropion-controlled trial with 1-year follow up.
Arch Intern Med
. 2006; 166:1561-1568.
Oncken C et al. Efficacy and safety of the novel selective nicotinic acetylcholine receptor partial agonist, varenicline, for smoking cessation.
Arch Intern Med
. 2006; 166:1571-1577.
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a